Phase equilibrium in the systems InAs₂S₃Se–InAs₂SSe₃, InAs₂SSe₃–In₃As₂S₃Se₃, InAs₂S₃Se–In₃As₂S₃Se₃,  InAs₂S₂Se₂–In₃As₂S₃Se₃, (InAs₂S₃Sе)_0.70(In₃As₂S₃Se₃)_0.30 (е₄)–(InAs₂SSe₃)_0.60(In₃As₂S₃Se₃)_0.40 (e₃)  were studied using the methods of physico-chemical analysis (DTA, X-ray phase, MSA, measurement of microhardness and determination of density) and state diagram was plotted. It was established that except the latter, all are quasi-binary and belong to eutectic type. The system InAs₂S₃Se–InAs₂SSe₃ is characterized by the formation of a new quaternary compound InAs₂S₂Se₂ melting congruently at 615 K. Liquidus surface projection of quasi-ternary system InAs₂SSe₃–InAs₂S₃Se–In₃As₂S₃Se₃ was constructed. Primary crystallization fields and co­or­dinates of non- and monovariant equilibrium were determined